Start moving the "activate configuration" script to be extensible.

svn path=/nixos/branches/fix-style/; revision=13675

system/activate-configuration.nix

@@ -0,0 +1,43 @@
+# generate the script used to activate the configuration.
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.stringsWithDeps) textClosureOverridable;
+  inherit (pkgs.lib) mkOption mergeTypedOption mergeAttrs mapRecordFlatten id;
+
+  textClosure = steps:
+    textClosureOverridable steps
+    (["#!/bin/sh"] ++ (mapRecordFlatten (a: v: v) steps));
+
+  aggregateScripts = name: steps:
+    pkgs.writeScript name (textClosure steps);
+in
+
+{
+  system = {
+    activationScripts = mkOption {
+      default = [];
+      example = {
+        stdio = {
+          text = "
+            # Needed by some programs.
+            ln -sfn /proc/self/fd /dev/fd
+            ln -sfn /proc/self/fd/0 /dev/stdin
+            ln -sfn /proc/self/fd/1 /dev/stdout
+            ln -sfn /proc/self/fd/2 /dev/stderr
+          ";
+          deps = [];
+        };
+      };
+      description = ''
+        Activate the new configuration (i.e., update /etc, make accounts,
+        and so on).
+      '';
+      merge = mergeTypedOption "script" builtins.isAttrs mergeAttrs;
+      apply = lib: {
+        inherit lib; # used to fetch dependencies.
+        script = aggregateScripts "activationScript" lib;
+      };
+    };
+  };
+}

system/activate-configuration.sh

@@ -1,20 +1,6 @@
 #! @shell@
 
-systemConfig="$1"
-if test -z "$systemConfig"; then
-    systemConfig="/system" # for the installation CD
-fi
-
-export PATH=/empty
-for i in @path@; do PATH=$PATH:$i/bin:$i/sbin; done
-
-
-# Needed by some programs.
-ln -sfn /proc/self/fd /dev/fd
-ln -sfn /proc/self/fd/0 /dev/stdin
-ln -sfn /proc/self/fd/1 /dev/stdout
-ln -sfn /proc/self/fd/2 /dev/stderr
-
+source @newActivationScript@
 
 # Set up the statically computed bits of /etc.
 staticEtc=/etc/static

system/options.nix

@@ -2912,6 +2912,8 @@ root        ALL=(ALL) SETENV: ALL
 
   require = [
     # system
+    (import ../system/system-options.nix)
+    (import ../system/activate-configuration.nix)
     (import ../upstart-jobs/default.nix)
 
     # newtworking

system/system-options.nix

@@ -0,0 +1,48 @@
+# this file contains all extendable options originally defined in system.nix
+{pkgs, config, ...}:
+
+let
+  inherit (pkgs.stringsWithDeps) noDepEntry FullDepEntry PackEntry;
+
+  activateLib = config.system.activationScripts.lib;
+in
+
+{
+  require = [
+    # config.system.activationScripts
+    (import ../system/activate-configuration.nix)
+  ];
+
+  system = {
+    activationScripts = {
+      systemConfig = noDepEntry ''
+        systemConfig="$1"
+        if test -z "$systemConfig"; then
+          systemConfig="/system" # for the installation CD
+        fi
+      '';
+
+      defaultPath =
+        let path = [
+          pkgs.coreutils pkgs.gnugrep pkgs.findutils
+          pkgs.glibc # needed for getent
+          pkgs.pwdutils
+        ]; in noDepEntry ''
+        export PATH=/empty
+        for i in ${toString path}; do
+          PATH=$PATH:$i/bin:$i/sbin;
+        done
+      '';
+
+      stdio = FullDepEntry ''
+        # Needed by some programs.
+        ln -sfn /proc/self/fd /dev/fd
+        ln -sfn /proc/self/fd/0 /dev/stdin
+        ln -sfn /proc/self/fd/1 /dev/stdout
+        ln -sfn /proc/self/fd/2 /dev/stderr
+      '' [
+        activateLib.defaultPath # path to ln
+      ];
+    };
+  };
+}

system/system.nix

@@ -196,10 +196,13 @@ rec {
   # The script that activates the configuration, i.e., it sets up
   # /etc, accounts, etc.  It doesn't do anything that can only be done
   # at boot time (such as start `init').
+  # DO NOT EXTEND THIS.  You should use the option system-option.nix
   activateConfiguration = pkgs.substituteAll rec {
     src = ./activate-configuration.sh;
     isExecutable = true;
 
+    newActivationScript = config.system.activationScripts.script;
+
     inherit etc wrapperDir systemPath modprobe defaultShell kernel;
     hostName = config.networking.hostName;
     setuidPrograms =
@@ -212,12 +215,6 @@ rec {
 
     inherit (usersGroups) createUsersGroups usersList groupsList;
 
-    path = [
-        pkgs.coreutils pkgs.gnugrep pkgs.findutils
-        pkgs.glibc # needed for getent
-        pkgs.pwdutils
-      ];
-
     bash = pkgs.bashInteractive;
 
     adjustSetuidOwner = pkgs.lib.concatStrings (map